1. Field of the Invention
Photographic apparatus having means for advancing a self-developing film unit from a stack of the same located in a cassette.
2. Description of the Prior Art
The present invention relates to photographic apparatus for advancing an instant or self-developing type film unit from a film cassette toward a pair of pressure-applying members. The film units are generally stacked within the film cassette with their leading ends located adjacent to a leading end wall of the film cassette and their trailing ends located adjacent to a trailing end wall of the film cassette. A platen is located between a bottom wall of the film cassette and the bottom film unit in the stack. The platen resiliently biases the stack toward a forward wall of the film cassette having a rectangular exposure opening therein such that the uppermost (endmost) film unit has (1) its photosensitive area in alignment with the exposure opening, (2) its leading end located in alignment with an egress in the cassette's leading end wall, and (3) its trailing end located adjacent an ingress located in a portion of the film cassette where its trailing end wall joins its forward wall. Mounted adjacent to the trailing end wall of the film cassette is a film advancing apparatus having a thin cantilevered member. This member is adapted to be moved into the film cassette (subsequent to the exposure of the uppermost film unit) via the ingress, so as to engage the endmost film unit by its trailing end and advance it toward the exterior of the film cassette via the egress.
From the foregoing it can be readily seen that the thickness of and the spacing between adjacent trailing ends of the film units is an important consideration in the design of the film advancing apparatus. As the thickness of the trailing end decreases, as well as the spacing between adjacent trailing ends, there arises a problem that the film engaging member of the film advancing apparatus may ride up over the thin trailing end and thus fail to advance the film unit from the film cassette. Or, the film engaging member may engage the trailing ends of the two uppermost film units in the stack thus moving an unexposed adjacent film unit as well as an exposed endmost film unit from the film cassette.